Recently got Walk Scape which is a rune scape inspired game, but you do things by walking and just reads from the google analytics on your walking distance, so no gps and doesn't care where you go, just that you walk. So like to mine something, you take 10 steps, and so on. Also really nice that if you complete your current task, your steps are stored. So you don't have to do things while on the walk, you pick stuff to do before you walk, and then check in after. Really enjoying it!
Also got an app called Macadam, which gives you prizes for walking. But the model is kinda annoying because you'll get 25 coins for walking 2,500 steps in a day, but then you'd get like 5k for doing surveys and 10k for "playing partner games". So it feels a bit just like a mist play clone with a pedometer.
I didn't like games like pokemon go because the best way to play was always just to drive to a good place and hang out there. Also it required you to stop while on your walk.
My wife and I have been playing Pikmin Bloom lately. It's from the same company as Pokemon Go, but focuses a lot more on the actual walking - there are battles kinda like gyms (mushrooms), but you don't need to hang around them at all (if you can see it on the map you can join) and you can even be invited to remote ones from friends. The other important points of interest - that are kinda like pokestops - are called "big flowers" and they require walking around them* to activate them, standing there won't do much.
There are tasks to complete for events or leveling up which directly require certain numbers of steps or indirectly require certain distance traveled at walking speed*
(*it's a little more involved but that's the high level overview)
Seconded for Pikmin Bloom. it really his am walking app as much as much as it is a game. I like Pokemon Go and Ingress too (from the same company), but this is the lightest weight, cutest, and most suited to being able to put it away during your walk if you want.